Yup, this is the flail set that many teams will fear if there is no entry hazard or priority attack.

After a Shell Smash, Crustle's attack reaches a 578 Atk, which will be enough to slaughter pretty much every pokemon in RU, followed by a decent 414 Spd. IV's in HP and defenses should be lowered to 0 which increases your chances of getting your HP to 1%(yay for sturdy!Free focus Sash). This will also activate the Custap/Salac Berry giving Crustle the Finishing power it needs.

Stealth Rock could be set up second turn if you don't get hit on the first. this will break the opponent's sash if they use one.

Earthquake is just for the Ghost pokemon and Steel pokemon that appear every now and then. Rock Blast is behind the slash because it can be used to break substitutes.

I really doubt you have tested this considering that both Custap Berry and Salac Berry have not been released yet.

The rest of the analysis isn't good either. The comments are lackluster, the use of words that are only used during speech like 'yup' and 'yay,' and SR should never be used by a Shell Smash sweeper. It's also very sad to see no STABs getting main slashes. What a waste of X-scissor and Stone Edge.

Agreeing with Darkmalice. Also, why in the world would you run Stealth Rock on a Shell Smash set?
"Stealth Rock could be set up second turn if you don't get hit on the first. this will break the opponent's sash if they use one."
You do realize that Crustle is slow as dirt, so this argument is invalid. Even if you do get a chance to use it, it would be infinitely better to run more coverage moves so you can actually attempt to sweep. The fact that the berries haven't even been released yet means that the best set you could pull off would be the Shell Smash Crustle set that is already in the Copyediting stage.

Wi-Fi Commissioner

Yeah, closing this and moving please learn the metagame you are trying to write for including what's illegal and legal (Salac and Custap berries are not released as one poster pointed out above). Also, there are formats for sets please read the announcements at the top of this forum.